Diamond Window Research Articles

Raman spectra of potassium carbonate and bicarbonate aqueous fluids at elevated temperatures and pressures: comparison with theoretical simulations

One-molal solutions of potassium carbonate and potassium bicarbonate were investigated by Raman spectroscopy from 22° to 550°C and from 1000 to 2000 bar. Experiments were performed in a special hydrothermal pressure vessel fitted with conical diamond windows. Frequencies and half-widths of the vibrational modes were measured for both carbonate and bicarbonate as a function of temperature and pressure. In the case of potassium carbonate solutions, dissolved bicarbonate appeared with its concentration dramatically increasing with increasing temperature and decreasing density. The opposite behavior occurred in the case of potassium bicarbonate: the relative concentration of dissolved carbonate increased relative to total bicarbonate. In addition, at temperatures above 300°C, dissolved aqueous carbon dioxide appeared with its concentration continuing to increase with increasing temperature and decreasing density. Simulations using theoretically-predicted mass action constants were used to compute changes in solution speciation for these solutions as they were subjected to increased temperature and pressure. Results resulting from these predictions matched those discovered in the spectral measurements.

High-Pressure Solution X-ray Scattering of Protein Using a Hydrostatic Cell with Diamond Windows

A hydrostatic high-pressure cell (maximum pressure 700 MPa) with synthetic diamond windows is applied to measure small-angle X-ray scattering of a protein at high pressure. Use of the present cell allows an accurate solvent background correction, providing quantitative analyses. The performance of the present cell for X-ray scattering is shown by using lysozyme as a sample solution. From the Guinier plot, values of the radius of gyration of lysozyme are evaluated to be 15.31 +/- 0.09 A at 1 atm (0.10 MPa) and 14.80 +/- 0.15 A at 400 MPa.

Status of electron cyclotron wave technology

A review of the two key technologies for the electron cyclotron wave (ECW) system, the gyrotron source and the window, is presented. In both fields, significant progress has been made to meet the requirements of the heating and current drive systems planned for devices such as W7-X or ITER, namely 1 MW-CW (continuous wave) in the frequency range 140-170 GHz. Gyrotrons in this performance range have been tested in long pulse operation (many seconds). With the use of a diamond window, extremely long pulse or true CW operation is possible. Tests presently underway confirm such a promising behaviour of the window, paving the way towards the development of megawatt CW tubes.

Spectroscopy of Hydrothermal Reactions. 10. Evidence of Wall Effects in Decarboxylation Kinetics of 1.00mHCO2X (X = H, Na) at 280−330 °C and 275 bar

Decomposition kinetics of 1.00 m formic acid and sodium formate to form CO2 (and H2) were probed under hydrothermal conditions of 280−330 °C and 275 bar. Flow reactor spectroscopy cells constructed from different metals (316 stainless steel, 90/10 Pt/Ir alloy, and grade 2 Ti) with diamond and sapphire windows were used to determine the rate of formation of CO2 in situ by IR spectroscopy. A single fluid phase was maintained. CO2 was produced at different rates depending on the metal and, in the case of 316 stainless steel, with a lot-dependent, concentration−time profile. The values of Ea = 87−121 kJ/mol resemble those previously reported for surface- and H2O-catalyzed decarboxylation of formic acid. Much higher Ea values are reported for unimolecular decomposition. Sodium formate decarboxylates more slowly than formic acid. In contrast to formic acid, the rate of decarboxylation of malonic acid in all of the cells is the same within error, which is consistent with a homogeneous unimolecular reaction.

The beamline SINBAD at DAΦNE

SINBAD, the first beamline in Italy designed to work in the far- and mid-infrared region, is being installed on DAΦNE storage ring, the new Φ-factory atLaboratoriNazionali di Frascati. DAΦNE, first injected in September 1997, will work at 0.51 GeV with a beam current in the range 2–5 A. The infrared synchrotron radiation extracted from a bending magnet is expected to be more brilliant than a black body at 2000 K up to three orders of magnitude in the wavelength range 10–1000 µm. The optical layout of SINBAD, fully designed by ray tracing simulation, includes six mirrors placed in a 18 m long beamline. The infrared radiation is first focused on a wedged diamond window and then re-focused on the entrance of aMichelson interferometer. Diffraction effects and mirror roughness, as well as optical aberrations, have been evaluated.

Diamond membranes: Applications for single ion detection using secondary electron emission

The assessment of mechanisms for radiation damage in both biological and semiconductor systems is much enhanced by ensuring that each cell or memory unit is hit by one and only one ion. Such “single ion” systems operate by detecting the passage of an ion and using the signal to deflect the beam upstream thus ensuring that only a single ion is injected to the system at a time. For biological investigations of the effects of single ion impact on living cells, the ion needs to be extracted from the vacuum of the accelerator through a thin window into the atmosphere. The requirements on such a window are: (a) that it be thin enough to allow the passage of the ion through it without excessive energy loss; (b) that it possess mechanical strength sufficient to survive the pressure differential; and (c) that upon passage of the ion through it, a sufficiently large signal is generated to ensure a 100% efficient detection of the passage of the ion. This set of demanding requirements can be met by a thin diamond window fabricated by CVD technique, taking advantage of the high secondary electron yield of B-doped diamond. In the present work, we report on the use of B-doped diamond membranes for this purpose.

Spectroscopy of Hydrothermal Reactions. 8. Kinetics of Aqueous NH(4)XCN (X = O, S) and OCS by Flow Reactor-Infrared Spectroscopy.

The kinetics and pathway of hydrothermolysis of 1 m NH(4)SCN to CO(2), NH(3), and H(2)S were determined at 543-573 K and 275 bar by the use of FTIR spectroscopy and a Pt/Ir flow reactor with diamond windows or a 316 stainless steel flow reactor with sapphire windows. The rates of SCN(-) loss and CO(2) formation were the same. The reaction is (pseudo) second-order with E(a) = 113 +/- 11 kg/mol and ln(A, kg/(mol.s)) = 21 +/- 2. DeltaS() = -84 J/(mol.K), which suggests a bimolecular, rate-determining, initial decomposition step for NH(4)SCN. A reaction scheme is proposed in which OCS and a monothiocarbamate species are undetected intermediates. The absence of OCS is explained by the rapid hydrothermolysis rate of OCS to CO(2) and H(2)S which was determined by IR spectroscopy at 393-423 K under 275 bar to be E(a) = 44 +/- 5 kJ/mol and ln(A/s) = 13 +/- 1 for OCS. The resulting rate is about 10(3) times faster than the hydrothermolysis rate of NH(4)SCN at 543 K. The results are compared to the equivalent reaction for NH(4)OCN. NH(4)OCN reacts about 3 x 10(3) times faster than NH(4)SCN at 543 K. The trend in the rates is consistent with the charge distribution and the trend in the bond distances, which resulted from ab initio quantum mechanical calculations at the HF/N311G//HF/N31G level in the OCN(-) and SCN(-) ions and the proposed carbamate and monothiocarbamate intermediates.

Expression of P40 homodimer of IL-12 in mouse sensory neurons

The design work for the ITER ECRH remote-steering upper-port launcher is described. The goal of the system is the stabilization of neoclassical tearing modes (NTMs). The required scanning range in the plasma (more than 20°) is achieved remotely, far away from the hostile plasma environment. This is done behind a diamond window in a separate vacuum environment. Scanning of the beam is done by a mirror that both rotates and translates to steer the beam in the proper way through the window and an isolation valve into a square corrugated waveguide. At the output of this 4.4 m long waveguide, the beam comes out at the same angle and is reflected by a fixed front mirror into the plasma [A.G.A. Verhoeven, et al., The ITER remote-steering ECW upper-port launcher, in: N. Hiromoto (Ed.), The 28th International Conference on Infrared and MM Waves, Otsu, Japan, September 29–October 3, 2003 (JSAP Catalog No. 031231)].

Complexing in Calcium Acetate and Propanoate Fluids at Elevated Temperatures and Pressures

The presence of saturated aliphatic carboxylic acids in low to medium temperature hydrothermal environments has been well documented. Experimental studies have demonstrated that acetic acid exists metastably to temperatures well above 300~ before undergoing decarboxylation (Palmer and Drummond, 1986). Similar expectations exist for propanoic and butanoic acids. Significant concentrations of acetic and propanoic acids have been measured in oil-field brines (Shock, 1994). Of particular interest has been the association of organic material with ore deposits such as the Mississippi Valley type. This has stimulated investigation of stability relations of metalic-organic complexes at elevated temperatures and pressures as such complexes may serve as major agents for the dissolution, transport and precipitation of the metals. Spectroscopic investigations of sodium and calcium acetate and propanoate solutions have been undertaken in order to investigate their relative stabilities and complexing behaviour as a function of temperature and pressure. Using a special hydrothermal pressure vessel fitted with conical diamond windows, Raman spectra of the acetate and propanoate solutions were measured at

Design of a single ion hit facility

The aim of this project is to develop a new system for single ion irradiation of cells for genetic and cell biology studies. This charged particle focused microbeam system will provide a fully computer controlled irradiation facility with submicron (subcellular) resolution and will open many new avenues into studies of radiobiological mechanisms. In the first stage of this project a system for single ion detection has been developed. A thin diamond window has been tested as vacuum/atmosphere window and as a possible source of secondary electrons and/or photons for single ion detection. A detection efficiency of 97% has been achieved.

Spectroscopy of Hydrothermal Reactions. 6. Kinetics and Pathway of Conversion of Carbohydrazide to CO2 and N2H4 at 503−543 K

Spectrokinetic analysis by IR spectroscopy was performed on 1.07 m carbohydrazide, (NH2NH)2CO, in a Pt/Ir flow cell with diamond windows. The reaction rate at five temperatures between 503 and 543 ...

A diamond-window XAFS cell for studies of high-temperature, high-pressure aqueous solutions

We describe a method to collect x-ray absorption fine structure (XAFS) spectra of ions in a supercritical water solvent. Supercritical water (SCW), at temperatures above water’s critical point of 374 °C, is an interesting solvent for chemical reactions and hazardous waste destruction due to the high solubility of organics and the aggressive oxidizing environment. XAFS may provide a better understanding of the solvent environment in SCW. The XAFS cell used in these studies was composed of a block of high-nickel alloy, Hastelloy C-22, containing two windows for transmission of the x-ray beam and a single optical view window. All internal wetted surfaces were platinum plated. The maximum operating conditions for this design were 500 °C and 700 bar. The x-ray transmission windows consisted of CVD (chemical vapor deposition) diamond windows (3 mm diameter ×0.5 mm thick) that were brazed to the tip of a standard 1/4-in. high-pressure, coned-shape fitting. Spectra are reported for strontium and rubidium ions in a supercritical water solvent. This cell design could be used for a variety of other solvent systems at high temperatures and high pressures.

Optical scattering of diamond films

One of the important applications for diamond films is the protective coating for optical windows, which require good transparency. Light scattering causes transmittance loss and cannot be ignored if the surface roughness or grain sizes are comparable with the wavelength. The microwave plasma technique was used to grow diamond films of well-defined {111} and {100} facets on silicon substrates by controlling the CH 4 H 2 ratio at 0.7% and 2.0%, respectively. The flow rate was 100 sccm and substrate temperatures were at 600 °C. An etched, free-standing window was used to study optical scattering by FTIR spectra and an integrating sphere. The FTIR transmittance spectra show that the scattering effect starts at a wavelength of around 5 μm, where well-grown crystallites appear. Such effect is even more serious for rougher {111} facets. This scattering can be eased by longer deposition and the so-called two-step process to obtain higher nucleation density. Optical properties of the diamond windows studied by integrating sphere show that only about 5% of incident visible laser beam is kept on its direction after passing the films, this number being somewhat higher for 1300 nm diode laser beam. Most of the loss can be attributed to body scattering inside the films. These results are in consistence with that of FTIR studies. It is safe to say that more directional trasmittance can be anticipated if a longer wavelength infrared beam is used as incident light source.

S1-2 Determinative role of N-myc in differentiation of the neural crest

The electron cyclotron heating and current drive (EC H&CD) upper launcher (UL) is a component of the ITER tokamak machine devoted to inject localized high microwave power, in order to counteract plasma instabilities (MHD activity). The UL consists of an assembly of ex-vessel waveguides (with diamond windows and isolation valves) and an in-vessel port plug (PP). The PP, with length close to 6 m, is fixed by a support flange into the upper port of the vacuum vessel (VV) as a cantilevered structure and the nominal gap between PP and port is 25 mm only. During an earthquake, accelerations generated by seismic events cause oscillations of the PP which might be amplified in case of resonance with the natural frequencies. A seismic analysis is therefore required in order to check the response of the UL PP to earthquakes.This paper shows the procedure used for the seismic analysis of the UL PP and results are given in terms of displacements and stresses. The ITER reference earthquake named SL-2 seismic event was considered. The response spectrum method was used in the analysis and floor response spectra (plots of acceleration versus frequency) provided by ITER/F4E at the upper level of the tokamak were applied to the supports as load. A seismic analysis of the UL PP integrated in the upper port is also here reported.The natural frequencies of the PP are far from the frequencies of the peaks in the applied spectra, so no resonance condition occurs. The obtained displacements and stresses of the PP are relatively small. The maximum total displacement is lower than 2 mm and the maximum equivalent stress is below 30 MPa. Since the highest excitation is the vertical one, most part of the total displacement is in the vertical direction. Afterwards, these results due to the seismic loads must be combined with displacements and stresses due to other loads affecting the PP such as the electromagnetic loads.

Spectroscopy of Hydrothermal Reactions. 5. Decarboxylation Kinetics of Malonic Acid and Monosodium Malonate

The kinetics of decarboxylation of 1.07 m malonic acid and monosodium malonate at 120−230 °C and 275 bar were determined directly in a combined microflow reactor and short-pathlength IR spectroscopy cell. Malonic acid and monosodium malonate decomposed in a single step to CO2 and acetic acid and CO2 and the acetate ion, respectively. The kinetics for malonic acid were modeled as an equilibrium between malonic acid and the monoanion with parallel decarboxylation of both species. The Arrhenius parameters are Ea = 120 ± 2 kJ/mol and ln A (s-1) = 29.4 ± 0.1 for the malonate monoanion and Ea = 126 ± 2 kJ/mol and ln A (s-1) = 31.4 ± 0.1 for malonic acid in a 316 stainless steel flow reactor at 120−210 °C. Decarboxylation of the monoanion is slower than that of malonic acid. The rates of decarboxylation of malonic acid are slower above 140 °C in a Pt/Ir alloy flow reactor with diamond windows than in a 316 stainless steel flow reactor with sapphire windows.

Oxidation of diamond windows

Diamond windows were heated at 700-900 °C in air for short times to better define the limits of application at high temperature. The infrared (IR) transmission of polished chemical vapor deposition (CVD) diamond windows was reduced after heating in a furnace at 800 °C for 75 s, while heating at 700 °C for 75 s produced little change. The 800 °C heating caused increased visible light scatter, and increased scatter appears to be mainly responsible for the reduced IR transmission. The forward scatter at 10.6 μm for the CVD diamond samples was 0.8% before heating, 2.8% after heating at 800 °C for 75 s, and 6.2% after heating at 800 °C for 255 s. Single crystal (110) type IIa diamond exhibited little change in IR transmission when heated at 800 °C in air for 255 s, while heating for 555 s at 800 °C caused a significant drop in IR transmittance (6-12%). A slight drop in IR transmittance (1-5%) occurred for a type IIa diamond when heated at 900 °C for 45 s. The etched surfaces were characterized by differential interference contrast optical microscopy, scanning electron microscopy, and Talystep surface profiles. Etched features are concentrated at grain boundaries (for the CVD samples) and at sites with residual damage from mechanical polishing that could not be seen before the heat treatment. Deep etch pits formed at grain boundaries that extend into the bulk of samples.

Measurement of Fluid Film Thickness on Curved Surfaces by Raman Spectroscopy

The Raman scattering intensity from a polyphenylether fluid film entrapped between a diamond window and a one-inch-diameter steel ball is found to correlate linearly with fluid film thickness over a 0.1 to 10 μm thickness range. The calibration and precision of the technique, as well as comparisons with other methods, are discussed.

A hydrostatic optical cell with synthetic diamond windows for quantitative infrared measurements of fluids

An optical cell with synthetic diamond windows that achieves hydrostatic pressures up to 600 MPa has been constructed. It is capable of being used for various quantitative optical measurements of fluids because of its accuracy in controlling the pressure generated and constant optical pathlength. Designing features and its performance are described. A particular application in the determination of the infrared absorption coefficient of symmetric stretching mode of liquid CS2 under pressure is presented.

On the use of diamond as a pressure calibrant for near-infrared FT–Raman microspectroscopy at high pressures

The pressure-induced shift of the Raman-active t2g phonon mode of the diamond windows in a commercial diamond-anvil cell, located at l332.5 cm−1 at ambient pressure, can be used as an in situ calibrant for near-IR FT–Raman microspectroscopy at high pressures. The measured pressures are considered to be accurate to within ±2 kbar throughout the 4–45 kbar range for which the associated pressure (P, kbar) vs. wavenumber (v, cm−1) relationship is P = 6.66v − 1335.9. Keywords: FT–Raman spectroscopy, diamond, high pressures.

Advanced electron cyclotron heating systems for next-step fusion experiments

Abstract Electron cyclotron heating (ECH) is one of the major candidates for heating and current drive on ITER (170 GHz) and W7-X (140 GHz). ECH is extremely attractive from physics and reactor engineering points of view, offering start-up assist, efficient and localized power deposition, simple and compact launching structures with high injected power density, and a simple interface with shielding and blanket. High unit power (1 MW or greater) and high efficiency (35% or greater) single-mode continuous-wave (CW) gyrotron oscillators are under development in order to reduce significantly the systems costs by reducing the size of the auxiliary support systems. 140 GHz gyrotrons with 0.55 MW output power in the Gaussian free-space TEM 0,0 mode with a pulse length τ up to 3.0 s and efficiency η of 42% are already commercially available (Gycom). Improved internal quasi-optical mode transducers generate the TEM 0,0 output mode with efficiencies of 90–95% and separate the electron beam from the r.f. beam, thus allowing the use of large CW relevant depressed collectors for energy recovery. Tube efficiencies around 50% have been already achieved at JAERI and KfK. Face cooled double-disk sapphire windows, cryogenically edge-cooled single-disk sapphire windows (liquid-nitrogen, liquid-neon or liquid-helium cooling), distributed windows (metal or ceramics) as well as diamond and silicon windows are under investigation in order to solve the window problem. Long-distance high-power millimeter wave transmission from the source to the plasma device with very low ohmic losses and high mode purity can be accomplished by (1) a closed, highly overmoded, circumferentially corrugated or dielectrically lined, tubular HE 1,1 -hybrid mode waveguide and (2) open quasi-optical TEM 0,0 transmission through a gaussian beam waveguide using focusing reflectors as phase-correcting elements. This paper reports the state of the art in gyrotron, window, transmission line and antenna development and discusses possibilities of ECH systems cost reduction.